The present invention relates to an apparatus for reinstalling a fuel element in a fuel assembly of a nuclear reactor.
More specifically, the invention relates to an apparatus for reinstalling a fuel element in the fuel assembly of a water nuclear reactor in the case where the assembly is constituted by a system of rod-type vertical fuel elements held in place by a rigid structure essentially constituted by two respectively upper and lower end plates interconnected by ties parallel to the fuel rods, said ties joining to the structural assembly spacing grids which are parallel to the end plates and are disposed at several intermediate levels between the said end plates, these grids ensuring a flexible securing of the fuel elements or rods.
Even more specifically, the object of the present invention is an apparatus for a fuel assembly of the type in which the lower end plate can be disassembled due to the presence of screws or nuts joining the lower end plate to the lower end of the ties of the fuel assembly.
Such an assembly is already described and claimed in French Patent application EN No. 78 08282 filed on Mar. 22, 1978 by the present Applicant and entitled "Remotely assemblable and disassemblable fuel assembly". This earlier-dated application also describes the tool permitting the disassembly of the plate after turning over the fuel assembly. Obviously, disassembly takes place underwater in a storage pond.
Thus, the object of the apparatus for reinstalling fuel elements is to permit on the one hand the taking hold of a fuel element in a storage rack and on the other the introduction and guidance of the fuel element in the fuel assembly. During this operation, the introduction tool must permit a certain forcing when the fuel element traverses each spacing grid and the raising of the fuel element by a random height in the case of jamming in order to permit a further fuel element introduction operation.
To obtain all these functions, the apparatus for reinstalling the fuel element comprises on the one hand a guidance plate which is placed at the lower end of the fuel assembly and which is thus substituted for the lower end plate, said introduction plate being provided with orifices having the same configuration as the orifices in the spacing grid and on the other hand a tool which is able to grip the lower end (the fuel assembly being reversed) of an element, of the introduction thereof in its place into the fuel assembly and the exertion of a certain force on the fuel element in order to permit the passage through the spacing grids.